THE PERMO-TRIASSIC BOUNDARY IN VOLCANOSEDIMENTARY SECTION OF THE WEST-SIBERIAN PLATE ACCORDING TO PALEOMAGNETIC DATA: (FROM STUDIES OF THE CORE FROM THE TYUMENSKAYA SUPERDEEP BOREHOLE SD-6)

Abstract

We report here the results of paleomagnetic studies of the core from the Tyumenskaya superdeep borehole SD-6 in the depth range 5662-7472 m (deposits of the Vityutin, Varengayakh, Pur, Khadyr'yakh, Korotchaevo, and Aimal' Formations). The rocks of the Vityutin, Varengayakh, and Pur Formations are unusable for solving magnitostratigraphic problems because of the absence of the characteristic magnetization component. For the Khadyr'yakh, Korotchaevo, and Aimal' Formations, magnetostratigraphic section was constructed and correlated with master magnetostratigraphic scales, using the characteristic component. It is shown that the volcanosedimentary section exposed by borehole SD-6 in the interval 6421-7502 m formed from the Upper Tatarian stage of the Late Permian to the Olenekian stage of the Early Triassic. On the basis of correlation, the following stratigraphy of the formations is suggested: Aimal' (7452-7355 m) - upper part of the Tatarian stage (Upper Permian); Aimal' (7355-7250 m) - lower part of the Induan stage (Lower Triassic); Korotchaevo (7250-6802 m) - upper part of the Induan stage (Lower Triassic); Korotchaevo (6802-6520 m) - lower part of the Olenekian stage (Lower Triassic); Khadyr'yakh (6520-6421 m) - upper part of the Olenekian stage (Lower Triassic). According to paleomagnetic data, the Permo-Triassic boundary passes in the roof of reverse polarity in the middle part of the Aimal' Formation (between 7383 and 7355 m).